1. Field of the Invention
The present invention relates to a cylinder for pressure media, in particular a hydraulic master or slave cylinder in motor vehicles, having a bleed element screwed into an aperture in the cylinder casing, which bleed element is sealed against the casing.
2. Background Information
With known master or slave cylinders in motor vehicles, the plenum is sealed by means of a screw-type bleed element which is screwed into a threaded aperture in the cylinder casing. Such bleed elements typically have conical sealing faces, which sealing faces are brought into contact with corresponding seal seats by the application of an axial force.
If these seal seats are made of plastic, they no longer offer sufficient resistance against the bleed elements at elevated temperatures. Consequently, the plastic begins to creep at the location in question and the connection is no longer tight. To alleviate this problem, a metal insert which serves as a seal seat for the bleed element is often placed in the plastic cylinder casing. However, there is then a risk of loss of seal between the plastic casing and the metal insert due to aging and the different deformation behaviors exhibited by the two materials under the influence of temperature.
The advantage of the conical seal seat is that only a few rotations are required to open the bleed element, making bleeding very easy.
To avoid the problems associated with the conical seal seats, Laid-Open German Patent Application DE-OS 195 16 389.3 teaches the use of a radial sealing ring. However, a greater number of rotations is required to open the bleed element with this solution than is the case with the conical seal seat.